Caspa is the Spanish word for dandruff, the white or yellowish flakes that shed from your scalp and land on your hair and shoulders. It’s one of the most common scalp conditions in the world, affecting roughly half of all people at some point in their lives. Caspa isn’t a sign of poor hygiene. It’s driven by a natural biological process on your scalp that sometimes gets out of balance.
What Causes Caspa
Your scalp constantly sheds dead skin cells, just like the rest of your body. Normally, these cells are tiny and invisible. But when the turnover speeds up, the cells clump together into the larger, visible flakes you recognize as caspa. Under normal conditions, about 487,000 cells per square centimeter shed from the scalp. During active dandruff, that number jumps to around 800,000.
The main driver behind this acceleration is a type of yeast called Malassezia that naturally lives on everyone’s scalp. It feeds on the oils your skin produces. When Malassezia populations grow to 1.5 to 2 times their normal levels, they break down scalp oils into byproducts that irritate the skin. Your scalp responds by speeding up cell production, and those rapidly produced cells don’t shed individually. Instead, they stick together and fall off as flakes.
Oil production plays a role, but it’s not the whole story. Some people with oily scalps never get dandruff, while others with normal oil levels do. Researchers believe the real issue is an imbalance in the scalp’s microbial environment, where the yeast outcompetes other beneficial microbes and triggers an inflammatory response.
Common Triggers That Make It Worse
Hormonal changes are a major factor. Dandruff often first appears at puberty, when oil glands become more active and create a more hospitable environment for yeast growth. Stress, cold weather, and infrequent washing (which lets oil and yeast build up) can also trigger flare-ups.
Diet may play a role too. In one case-control study, about 17% of people with seborrheic dermatitis (a more severe form of dandruff) reported that sweets worsened their symptoms. The same study found that total sugar intake was significantly higher among people in the dandruff group compared to controls. Spicy food, fried food, and dairy products were also commonly reported as triggers, though individual responses vary widely.
What Caspa Looks and Feels Like
The classic signs are white or slightly yellow flakes on your scalp, in your hair, and on dark clothing. Your scalp may itch, sometimes intensely. In mild cases, you’ll notice small, dry flakes. In more pronounced cases, flakes become larger and greasier, and the underlying scalp can look pink or mildly inflamed.
Dandruff tends to stay within the hairline. If you notice thick, silvery scales that extend past your hairline onto your forehead or behind your ears, or if the patches look drier and more sharply defined, that pattern is more consistent with scalp psoriasis. Both conditions cause flaking and itching, but psoriasis scales typically look thicker and may appear on other parts of the body as well. If you’re unsure which you’re dealing with, a dermatologist can usually tell by looking at the scalp.
How to Treat Caspa Effectively
Most dandruff responds well to medicated shampoos you can find over the counter. The key is using the right active ingredient and giving it enough contact time. Most people make the mistake of applying the shampoo and rinsing it off immediately. For the active ingredients to work, you need to leave the shampoo on your scalp for at least 5 minutes before rinsing. For stubborn cases, applying shampoo to a dry scalp for up to 30 minutes before washing can boost effectiveness.
The three most common active ingredients work in slightly different ways:
- Zinc pyrithione (1%) controls yeast growth and reduces flaking. It’s the active ingredient in many everyday dandruff shampoos and is gentle enough for frequent use.
- Selenium sulfide (1-2.5%) slows down scalp cell turnover in addition to fighting yeast. It can slightly discolor light or color-treated hair, so rinse thoroughly.
- Ketoconazole (1-2%) is a stronger antifungal that directly targets Malassezia. In a large clinical trial of 575 patients with moderate to severe dandruff, using a 2% ketoconazole shampoo twice weekly for 2 to 4 weeks produced an excellent response in 88% of participants.
For initial treatment, plan to use a medicated shampoo two to three times per week for about a month. Most people see a noticeable reduction in flaking within 2 to 4 weeks. Once the dandruff clears, switching to once-weekly use of the same shampoo helps prevent it from coming back. If you stop entirely, the yeast will eventually repopulate and flaking will return, since dandruff is a recurring condition rather than something you cure once.
Natural Options That Have Evidence
Tea tree oil is the best-studied natural alternative. In a randomized controlled trial, a shampoo containing 5% tea tree oil reduced dandruff severity by 41%, compared to just 11% improvement with a placebo shampoo. Participants also reported less itching and greasiness, with no adverse effects. You can find tea tree oil shampoos in most drugstores, or add a few drops of pure tea tree oil to your regular shampoo. Concentrations around 5% appear to be the effective threshold.
Apple cider vinegar and coconut oil are popular home remedies, but neither has the same level of clinical evidence. Coconut oil may help with dryness but won’t address the underlying yeast overgrowth. If your dandruff is mild and mostly cosmetic, natural options may be sufficient. For persistent or moderate flaking, a medicated shampoo will deliver faster, more reliable results.
Why Caspa Keeps Coming Back
Dandruff is a chronic condition, not an infection you clear and forget. The Malassezia yeast is a permanent resident of your scalp. When conditions favor its growth (more oil, stress, seasonal changes, skipping treatment), flaking returns. This is why dermatologists recommend ongoing maintenance with a medicated shampoo even after symptoms improve. In the ketoconazole trial, once-weekly prophylactic use was effective at preventing relapse. Think of it less like taking a course of medication and more like a long-term grooming habit, similar to how you’d manage oily skin with the right cleanser.